1. Field of Invention
The present invention relates to a medium detection method and a medium processing device that determine if the medium is skewed as it is conveyed through the transportation path in a medium processing device that processes while conveying media such as checks through a transportation path.
2. Description of the Related Art
In banks and other financial institutions, checks, promissory notes, and other check-like negotiable instruments (collectively referred to as “checks” herein) submitted for payment or processing are loaded into a check reading device to capture images of the front and back and read the magnetic ink character line. As electronic processing of such instruments has become more common, the captured image data and magnetic ink character data is processed by computer, and the check information is managed by computer.
A typical check processing device reads the magnetic ink character line and captures images of the front and back of each check as the checks are conveyed horizontally standing on edge through a transportation path that is a narrow vertical channel open to the top passed a magnetic head and image sensors (image scanning heads). The downstream end of the transportation path is connected to a first storage pocket (first discharge unit) and a second storage pocket (second discharge unit). Checks from which the magnetic ink character line is read normally are discharged into the first storage pocket, and all other checks are discharged into the second storage pocket. Checks that are discharged into the second storage pocket are conveyed and processed again. A check processing device of this type is taught in Japanese Unexamined Patent Appl. Pub. JP-A-2004-206362.
When checks are multifed, or when a check is fed with the top and bottom or front and back reversed, in a check processing device, the magnetic ink character line cannot be read or read errors occur. To detect such transportation errors, Japanese Unexamined Patent Appl. Pub. JP-A-2005-225661 teaches a check processing device that has a detection unit to detect multifeed states in which two or more checks are simultaneously conveyed overlapping, and Japanese Unexamined Patent Appl. Pub. JP-A-2008-117040 teaches a check processing device having a detection unit to detect when a check is conveyed with the top and bottom inverted or the front and back reversed.
If a check is conveyed in a skewed state at a great angle of inclination to the transportation path, the check is conveyed with the printing position of the magnetic ink character line removed from the reading position of the magnetic head, and the magnetic ink characters either cannot be read or read errors occur. In order to detect if a check is conveyed in a skewed position, the timing when the paper medium passes the respective detection positions may be detected by a pair of photosensors that are separated perpendicularly to the transportation direction detect, and a skewed feed state may be detected when there is a great difference in the timing when the medium passes the sensor pairs as taught in Japanese Unexamined Patent Appl. Pub. JP-A-H06-9105.
When skewed transportation of the check medium is detected using the method taught in Japanese Unexamined Patent Appl. Pub. JP-A-H06-9105, the following problems can occur.
The edges or corners of the check may become folded and creased while in the possession of the user, such as when the check is inserted to the user's wallet or coat pocket. If the check is then loaded into the check processing device, the check may be conveyed folded over along the crease. If the check is conveyed with one side at the leading end in the transportation direction folded over, the timing when the one sensor disposed to the position where this folded part passes detects the check will be delayed from the timing when the other sensor detects the check. If this delay is great, a skewed transportation condition may be detected even though the check is conveyed in a normal unskewed condition. It is also conceivable to detect the length of the passing check by means of these sensors and detect if the check is skewed based on the difference in the detected lengths. However, if one of the ends is folded over, the detected lengths will be accordingly different, and detection errors may result. More specifically, the detected length will be short by the amount that the check is folded over.